1. Field of the Invention
The invention is directed to a chemical injection valve for regulating the flow of chemicals or other fluids from the exterior of well tubing to the interior thereof.
2. Prior Art
It is sometimes necessary to treat wells by injecting into the production tubing certain chemicals, fluids and/or hot oil. Hot oil is used to melt paraffin that has built up on the walls of the tubing.
In order to introduce these fluids into the production tubing it is common to flow the fluids into the casing-tubing annulus and meter the treating fluid into the tubing through some valve device attached to the tubing. The point of fluid entry is commonly a mandrel, connected in the tubing string, onto which is attached some fluid regulating device. Typical of the mandrels useful for this purpose is the Type B conventional gas lift mandrel manufactured by Otis Engineering Corporation, illustrated in their Gas Lift Equipment and Services catalogue OEC-5122b, page 28. A currently used chemical injection valve manufactured by Otis Engineering Corporation is their "NCV" valve, having assembly number 221 NCV 1001. This valve is a spring loaded ball valve connectible to the Type B conventional gas lift mandrel.
As a rule, chemical injection valves used currently have a metal to metal abutment type valve and valve seat. Pressure differentials between opening and closing of the valve against the seat usually cause dumping of the fluid being injected. As a consequence, it is difficult to obtain a true metering of injected chemicals. For proper treating of wells, using a chemical injection valve, it is desirable to have a rather constant, metered flow of injection fluid.
It has been a goal of the industry to have a single injection valve that can both meter constant, regulated flow of fluids while being capable of rapidly injecting large quantities of fluid, such as would be required to kill a well.
Therefore, it is an object of the invention to provide a chemical injection valve which will provide a constant, metered flow of fluid.
It is a further object to provide a chemical injection valve that will permit a large flow of injected fluid therethrough.
Another object is to provide a chemical injection valve having a constant back pressure operating to resist flow of fluid through the valve.
Yet another object is to provide a chemical injection valve that does not have a metal to metal valve and seat arrangement.
It is a further object of the invention to provide a chemical injection valve having a close fit spool and cylinder valve arrangement without seals for metering injection fluids.
The above and other objects and features of the invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred embodiment of the invention is shown.